1. Field of the Invention
The present invention relates to a flicker detection system for an apparatus in which a lamp is used, such as a projector or the like, a method of detecting flicker, and a projector apparatus.
2. Description of the Related Art
It has been common to employ a discharge lamp such as a Xenon lamp etc. (hereinafter referred to simply as a lamp) having advantages of serving substantially as a point-source light and providing a high luminance for projector apparatuses such as a LCD (Liquid Crystal Display) projector, a DLP (Digital Lamp Processing) projector, etc. The luminance of a lamp ordinarily decreases with usage (operation time) causing the projected picture to become unclear. In order to address such an issue, Japanese Patent Laid-open Publication No, 2001-142145 describes measures to estimate in advance the usable life of a lamp, i.e., the time that elapses until the luminance is reduced causing the projection picture to become difficult to view, so that the lamp can be used for a maximum time.
In addition to the reduction of the luminance of a lamp, on the other hand, another cause that is responsible for disturbance in viewing the projection picture is the occurrence of flicker. Conventionally, manufacturers determined the life of a lamp based upon commonly performed tests to estimate reduced luminance and the occurrence of flicker to measure the approximate elapse of time until lamps would become unusable. Further, this information about the estimated life of a lamp was inputted into projector apparatuses as data which set the same limit on the usable time of individual lamps.
This above mentioned method to determine the usable life of a lamp was based upon the tendency of lamp in general and not on an individual lamp by lamp basis.
Furthermore, as a means to reduce the running cost a projector apparatus, there is a recent requirement on the part of users to continue using the lamp as long as the projection picture is reasonably clear, regardless of reduced luminance which results from long time use. A common practice in cinema theaters where films are shown is that lamps are replaced whenever there is an occurrence of flicker. As a result, the usable life of a lamp that has been inputted into the projector apparatus in advance as data is only regarded as a rough standard, and in fact the lamp is actually used until flicker occurs.
In the case of a Xenon lamp, on the other hand, the increase of flicker increases the risk that the lamp will burst. Consequently, any delay in replacing the lamp could cause the lamp burst within the projector apparatus. What is needed is a safe and reliable means to protect the projector apparatus from the bursting of a lamp in situations where the lamp is used until almost the expiration of the lamp.